By Colin Moore, Ketty Loeb, Victoria Keener, and Zena Grecni

Hawaiʻi is among the most vulnerable places in the United States to sea level rise. Nearly all residents live near the coast, where housing, transportation networks, tourism infrastructure, and cultural sites are concentrated. Chronic flooding and beach erosion are already visible in many communities, and long-term projections point to steadily rising risks over the coming decades.

Until recently, however, there has been little systematic evidence on how residents view this threat or what kinds of policy responses they are prepared to support. To address this gap, an interdisciplinary team from Pacific RISA, UHERO, and the UH Institute for Sustainability and Resilience conducted Hawai‘i’s first statewide, representative survey of public attitudes toward sea level rise (SLR) in summer 2025, gathering responses from 1,314 adults across all four counties. The results provide a baseline picture of public beliefs, risk perceptions, and policy preferences at a critical moment for coastal planning in the state.  Detailed findings are presented in the full report, Public Views on Sea Level Rise in Hawaiʻi: Results from a Statewide Survey.

Three themes stand out:

• unusually broad agreement that sea level rise is happening,
• a strong sense of urgency about its impacts, and
• uncertainty about how long-term adaptation should be financed.

Taken together, these findings indicate that Hawaiʻi’s primary challenge lies not in public awareness, but in governance and the financing of long-term adaptation.

Key findings

• 89 percent of residents believe sea level rise is happening.
• Majorities of Democrats (97 percent), Independents (90 percent), and Republicans (80 percent) agree.
• 49 percent say SLR is already affecting people in Hawaiʻi; 82 percent expect impacts within 25 years.
• 83 percent believe impacts will be catastrophic within 50 years.
• Roughly 90 percent support restricting development in flood-prone areas.
• 81 percent would relocate from high-risk areas if offered fair compensation.
• Only 45 percent are willing to pay higher taxes or fees for neighborhood-level protection.

Widespread public agreement

Public belief that sea level rise is occurring is widespread in Hawaiʻi. Statewide, 89 percent of residents say that sea level rise is happening (Figure 1). This view is shared at similarly high levels across all counties, ranging from 88 percent in Honolulu and Kauaʻi to 92 percent in Maui. In other words, belief in sea level rise is not confined to particular islands or communities but is broadly distributed across the state.

What makes this especially notable is how little this belief varies across political lines. Ninety-seven percent of Democrats say sea level rise is happening, but so do 90 percent of Independents and 80 percent of Republicans. Large majorities of both liberals and conservatives express the same view.

Residents are somewhat less unified on the causes of sea level rise, but disagreement remains limited. About two-thirds attribute SLR to a combination of human activity and natural processes, and another fifth see it as mainly human-caused. Only a small minority attribute it solely to natural processes.

From a policy perspective, this matters. Broad agreement that the problem exists lowers the political costs of acknowledging risk and creates space for long-term planning that would be far more difficult in a polarized environment.

Sea level rise as a present threat

Hawaiʻi residents also view the impacts of sea level rise as imminent.

As Figure 2 shows, nearly half say SLR is already affecting people in the state. Another 19 percent expect impacts to begin within the next ten years. In total, more than four in five residents anticipate local impacts within the next 25 years.

Expectations about personal exposure are similarly high:

• 20 percent say they or their family have already been affected through flooding, higher insurance costs, or property damage.
• 32 percent expect to be affected within ten years.
• 20 percent expect impacts within 25 years.

Concern about long-term severity is widespread. Eighty-three percent agree that sea level rise will have catastrophic consequences for Hawaiʻi within the next 50 years.

When asked about specific outcomes if no action is taken, large majorities expect coastal erosion and beach loss, frequent flooding, damage to coastal property and infrastructure, disruption to tourism areas, losses to natural resources and cultural sites, and impacts on agriculture and public health.

For many households, these risks are already financial as well as physical. Thirty-nine percent report increased costs related to sea level rise or coastal flooding, including housing expenses, insurance premiums, repairs, or business disruptions.

In short, sea level rise is not viewed as an abstract future problem. It is widely understood as a present and near-term challenge to communities, livelihoods, and the state’s economic base.

Strong support for acting—and for changing how Hawaiʻi builds

Given these perceptions, it is not surprising that residents want the government to respond. Nearly 90 percent say state leaders should act immediately to prepare for sea level rise, with more than half expressing this view strongly.

Support is especially high for policies that reduce long-term exposure to coastal hazards:

• about 90 percent support restricting new development in flood-prone areas;
• more than 80 percent favor prioritizing inland development over continued coastal expansion;
• roughly 80 percent support using public funds to acquire coastal land for conservation and restoration.

Residents also back an active government role in helping property owners manage rising risk. Large majorities support expanding eligibility for a state-funded flood insurance program, offering tax incentives or financial assistance to elevate or flood-proof buildings, and providing public funding to help owners relocate from flood-prone areas.

As Figure 3 shows, 81 percent say they would be willing to move away from areas identified as vulnerable to sea level rise if offered fair compensation.

This combination of preferences is unusual. In many coastal regions, public opinion strongly favors protection over retreat, even where long-term risks are severe. In Hawaiʻi, residents appear open to a mixed strategy that includes both helping people remain in place where feasible and supporting relocation where risks become unmanageable.

Views are more divided on shoreline armoring. A narrow majority (54 percent) believe private property owners should be allowed to build seawalls even if doing so harms public resources. Support is much stronger, however, for seawalls that protect public infrastructure such as roads, utilities, and harbors.

Overall, the survey points to a public that is receptive to significant changes in land-use planning and coastal management—an essential condition for effective long-term adaptation.

The central constraint: who pays?

While support for adaptation is widespread, there is no clear consensus on how it should be financed.

When asked whether they would be willing to pay higher taxes or fees to fund neighborhood-level protection from sea level rise, a majority of residents say no. Statewide, 55 percent are unwilling to pay more, while 45 percent say they would (Figure 4).

This gap between strong support for adaptation policies and reluctance to bear direct financial costs highlights the core governance challenge facing Hawaiʻi.

Many of the strategies residents endorse—relocating households, purchasing coastal land, reinforcing infrastructure, redesigning drainage systems, and maintaining protective ecosystems—require large and sustained public investment. While the survey did not test support for specific financing options, it does suggest limited public willingness to accept higher taxes or fees. Without credible, durable funding mechanisms, adaptation risks becoming a cycle of planning exercises and short-term projects rather than a coordinated long-term strategy.

Implications for policymakers

The survey results place Hawaiʻi in a distinctive position.

Unlike many states, policymakers do not face widespread skepticism or ideological resistance to acknowledging sea level rise. Public agreement on the reality and seriousness of the threat is broad, stable, and cross-partisan. Residents also support many of the most powerful policy tools available, including restrictions on coastal development and public assistance for relocation.

This creates a valuable window of opportunity.

At the same time, the financing problem looms large. Public reluctance to accept higher taxes or fees means that the hardest political work lies not in persuasion, but in designing cost-sharing arrangements that are seen as fair, credible, and effective.

That may require targeted state funding mechanisms, greater reliance on federal infrastructure and disaster-mitigation programs, clear prioritization of which areas can realistically be protected long term, and transparent communication about tradeoffs, limits, and timelines.

Sea level rise is a structural challenge, not a temporary shock, and it demands institutions and funding streams that reflect that reality.

Hawaiʻi does not lack public awareness or concern. What remains unresolved is how the costs of adaptation will be shared across communities, taxpayers, property owners, and future generations. How that question is answered will likely determine whether today’s strong public consensus translates into sustained, effective action—or remains a shared recognition of risk without the tools and funding needed to meet it.

This summary blog was originally published by the Economic Research Organization of the University of Hawaiʻi (UHERO) on Feb 16, 2026.

The full report is available on the UHERO website at: https://uhero.hawaii.edu/public-views-on-sea-level-rise-in-hawaiʻi-results-from-a-statewide-survey/

Coastal flooding in Palau is already affecting daily life—overtopping roads, disrupting access, and threatening critical and culturally important places. In partnership with Pacific RISA, Hawaii Sea Grant and the University of Hawaiʻi Sea Level Center (UHSLC), this work supports partners in in developing practical, place-based flood indicators that translate sea level and tide information into clear, decision-relevant insights for locations identified as vulnerable.

Over 10 days in January, Coastal Adaptation Specialist Moehlenkamp helped support field visits where a team collected 120 high-accuracy elevation measurements across Koror, Babeldaob, and Peleliu to support flooding threshold analysis. These measurements help link what communities observe on the ground with what tide gauge records show over time—so communities and agencies can better understand how severe flooding has been at specific places in the past, and how the frequency and depth of those events are likely to change as sea levels continue to rise.

From interviews to a priority site list

This field data collection effort was built on a stakeholder-driven process. An initial list of flood impact locations was compiled through interviews and meetings with community members, and stakeholders across the NGO, private, and government sectors. Those conversations identified roads, causeways, schools, taro fields, cultural sites, and other places where flooding creates real impacts. That list was then refined in collaboration with the Office of Climate Change (OCC) and the Palau Automated Land and Resources Information System (PALARIS) focusing on priority sites where elevation data could most directly support flood thresholds and locally usable indicators.

Field visits with local coordination and context

With support from the OCC, Coastal Adaptation Specialist Moehlenkamp visited sites and helped coordinate on-the-ground engagement. At many locations, the team met with state governors and/or state Protected Areas Network (PAN) coordinators, who guided them to the precise points to measure, and who also shared valuable context on flooding history and community impacts. These brief site meetings helped ensure the elevation measurements are not only technically accurate, but also locally meaningful and directly useful for the communities most affected.

What these measurements enable: localized flood indicators

Unlike broad flood risk assessments, this approach is designed to produce highly localized results. By linking high-accuracy elevation measurements at flood-prone sites with long-term tide gauge records, the analysis can evaluate a specific location—such as a road segment, school, or other critical site—and estimate:

• Historical flooding frequency (how often water levels likely exceeded a site’s flood threshold)
• Severity (how far above the threshold water levels reached during exceedances)
• Future changes in frequency and severity under different sea level rise scenarios

This level of detail can support both community and government decision-making, strengthen national adaptation planning, and inform updates to regional planning products and assessments.

One key finding is just how disproportionate the impacts are. Between 1980 and 2019, invasive species caused more than $11.7 billion in damages across US and US-affiliated islands. When adjusted for land area, that’s five times higher per square kilometer than on the US continent. Islands import most of their food and goods, rely heavily on tourism and military transport, and often have limited resources to respond when new pests arrive.

But the paper also shows that the biggest challenges are not about a lack of tools or knowledge. This research, led by Pacific RISA PI Laura Brewington as part of her service on the US Invasive Species Advisory Committee, identifies three lessons that apply not only to US islands, but to island nations around the world. First, local capacity and trust determine whether efforts succeed. Programs that invest in local jobs, training, and community engagement are more likely to detect invasions early, while long-term support of island-led research, workforce development, and implementation supports sustained management as climate extremes intensify. Second, prevention at ports of entry matters. Airports, seaports, and shipping routes are the main gateways for invasive species. When inspections are inconsistent or under-resourced, new pests slip through—and the costs multiply later. Third, long-term control tools are essential but often underused. Islands have successfully applied biological control, targeted chemical treatments, and ecosystem restoration, but these approaches are frequently limited by short-term funding or regulatory delays. Expanding access to conservation-relevant tools and investing in restoration infrastructure also both increase ecosystem resilience following disturbance.

“In many cases, the science exists and the solutions are known,” says lead author Laura Brewington. “The real challenge is making sure systems are in place to prevent invasions in the first place and to act quickly and effectively when they occur.”

The paper also highlights promising examples, from interagency agreements in the Pacific to biofouling controls in Australia and community-driven biosecurity efforts in Mexico. These cases show that coordination and sustained investment can make a real difference. Islands are often described as “sentinels” for environmental change. But in the case of invasive species, they are also shields—protecting surrounding regions from further spread. Strengthening island biosecurity isn’t just an island issue. It’s a global one. Download the paper here.

Featured image: Sunset over Tumon Bay, Guam. Credit: Laura Brewington

]]> 7326 https://www.pacificrisa.org/2025/05/14/new-report-details-climate-change-challenges-and-adaptation-strategies-for-the-marshall-islands/ Wed, 14 May 2025 21:30:02 +0000 https://www.pacificrisa.org/?p=6983 Read More]]> Growing challenges from sea level rise and risks to water and food security and human health are among the major issues detailed in a new report on climate change in the Republic of the Marshall Islands (RMI). Considerations for managing threatened resources, including fresh water, fisheries, and infrastructure, are outlined in the report by the Pacific Islands Regional Climate Assessment (PIRCA), a consortium of several government, NGO, and research entities.

Climate Change in the Republic of the Marshall Islands: Indicators and Considerations for Key Sectors is one in a series of PIRCA reports. Authors from Arizona State University, the East-West Center, the Majuro Weather Service Office, and the University of Hawaiʻi—along with 29 technical contributors from local government, NGOs, and research—collaboratively developed the RMI PIRCA report.

Key Messages

Climate Change in the Republic of the Marshall Islands lays out the changes the country is already experiencing, and what lies ahead. The key messages for decision-makers include:

• Sea level rise threatens infrastructure, food and water security, and important ecosystems and cultural sites. Frequent and extensive flooding, coastal erosion, and saltwater contamination of groundwater are expected as sea level rise accelerates, threatening the long-term habitability of the atoll nation.
• Ocean changes disrupt fisheries and cause coral loss. Coral reefs are key to the Marshall Islands’ fisheries and protection from coastal flooding. Fisheries changes and extensive coral loss are possible within the next few decades if current trends in rising ocean temperatures continue.
• Hotter days and nights and stronger storms affect human health. Temperatures have risen, and heat waves stress water supplies and exacerbate a range of pre-existing health issues. More intense tropical cyclones mean a greater potential for flooding and associated public health and safety risks.
• Collaborations and increased climate finance can bolster resilience. National government, international partners, non-governmental organizations, and local communities can work to expand adaptation strategies and access to climate finance, which is needed to meet the scale of challenges facing the RMI.

About Climate Change in the Republic of the Marshall Islands and the PIRCA

The collective efforts of the technical contributors and coordinating authors made the RMI PIRCA report possible. The report builds upon the US National Climate Assessment, offering a closer look at climate change impacts in the RMI and providing information for a wide range of sectors.   

The PIRCA is funded and supported by Arizona State University’s Global Institute of Sustainability and Innovation, the US National Oceanic and Atmospheric Administration’s CAP Program (through Pacific RISA), and the East-West Center’s Research Program.

Cover photo: An aerial view of Majuro shows that atolls are primarily covered with forest or agroforest, surrounded by shallow reef. Photo courtesy of USGS project, “‘Vegetative Guide & Dashboard’ relating atoll traditional agroforestry recommendations to predicted climate and sea level conditions in the Marshall Islands.”

SEA technology is also generalizable across geoscience domains, through a framework called an Intelligent Data Exploring Assistant (IDEA), which can be demonstrated by asking it to analyze atmospheric observations from Mars collected by NASA’s InSight Mission (Try it!). By combining LLM capabilities with robust domain-specific customizations, SEA and the IDEA example generate accurate analyses, visualizations, and insights through natural-language prompts. This study highlights the potential of IDEA frameworks to lower technical barriers, enhance educational opportunities, and transform geoscientific workflows while addressing the limitations and uncertainties of current LLM technology. PI Widlansky’s work also highlights how AI can enhance scientific research and communication, and helps us to envision how the creation of similar tools can support scientists in many fields.

SEAinfo page, with several YouTube video demonstrations and presentations by PI Widlansky
https://uhslc.soest.hawaii.edu/research/SEAinfo/
GitHub IDEA page
https://github.com/uhsealevelcenter/IDEA
IDEA manuscript with a plain language summary and abstract
https://uhslc.soest.hawaii.edu/research/SEAinfo/IDEA_manuscript_latest.pdf

However, invasive species pose a significant threat to these islands, causing damage so severe that it is second only to climate change. Invasive species are responsible for nearly 90% of recorded species extinctions on islands and have caused billions of dollars in damages. The economic impact on U.S. and U.S.-affiliated islands is significantly higher than on the continental U.S., partly due to the high burden of invasive species on islands like Hawaiʻi. As an added threat, invasive species on these islands are merely one flight away from continental areas where they are not already established, posing immense risks to agriculture, industry, and biodiversity on the U.S. continent.

“U.S. and U.S.-affiliated islands are strategic strongholds for national security, global biodiversity, and economic stability—yet they remain uniquely vulnerable to invasive species. Federal leadership and investment in biosecurity will ensure these critical regions remain resilient and sustainable.” ~ Laura Brewington, the paper’s lead author

The high costs of invasion

Because many islands are geographically isolated, they are also highly susceptible to invasive species. Indigenous communities historically sustained themselves with minimal external influence, but modern trade and travel have increased the risk of invasive species introductions. The authors found that invasive species have cost U.S. and U.S.-affiliated islands over $16 billion in cumulative damages over the past 40 years. For instance, the State of Hawaiʻi has an almost equal number of nonnative plant species as the entire continental U.S., despite its small size. Invasive species reduce climate resilience by altering ecosystem structure and function, negatively impacting livelihoods, quality of life, food security, and culture.

Recommendations for federal action

The authors outlined four priority action areas where the U.S. federal government could begin to address these challenges to islands: terrestrial biosecurity, marine biosecurity, control measures and long-term impact reduction, and social and capacity conditions. For example, improved prevention efforts and jurisdictional coordination are needed to address terrestrial invasive species. Federal and local agencies should collaborate to enhance prevention at ports of entry. U.S. and U.S.-affiliated islands contain significant marine resources, including coral reefs, which are threatened by invasive species. Improved marine biosecurity measures are essential to protect these ecosystems.

Meanwhile, many islands already suffer from a high burden of invasive species. In these locations, biologically based control technologies and chemical controls are crucial tools for managing invasive species and must be developed with local conditions and capacity in mind. Post-disturbance restoration efforts will also be needed to recover ecosystems affected by invasive species, such as wildfire prone areas in Guam or Hawaiʻi. In all islands, federal agencies need to offer more support local capacity for invasive species management: investments in education, outreach, and professional development are essential to build local expertise and trust.

Federal agencies must address the urgent need for coordinated efforts to manage invasive species on U.S. and U.S.-affiliated islands, and this white paper offers a blueprint for how to do so in ways that are appropriate to the needs and challenges facing islands today. These efforts will be vital for enhancing climate resilience, protecting biodiversity, and supporting the well-being of all U.S. island communities.

Featured image: Pampas grass, an invasive grass in all the main islands of Hawaiʻi and other parts of the Pacific Islands. Image credit: Maui Invasive Species Committee.

After learning during the 2024 climate services dialog in Palau that taro (kukau, in Palauan) is a staple crop of high importance for food security and island sustainability, the team developed a prototype of an early warning dashboard for taro producers, who are primarily women as heads of households. During this visit, the goal was to evaluate ways to improve the draft dashboard and enhance its practicality for users. Information below was primarily gathered through taro patch visits with farmers, but also includes information gathered during meetings with NGOs, as well as government officials. Nearly all taro patches in Palau depend on surface water availability, so knowledge of rainfall amounts and frequency, as well as temperature and duration of hot and sunny weather, is crucial for making planting decisions or other interventions, such as when to cover vulnerable crops. With this information, the team will update the dashboard and integrate other suggested tools, such as a community news page for information exchange.

Summary

Studies have demonstrated that climate change is likely to impact mountain ecosystems across the globe, most typically through changes in temperature and shifts in water and nutrient availability, which could lead to upward shifts in species ranges over time. It is unclear, however, the extent to which plant species are shifting their ranges upslope in Hawaiʻi, and whether the rate of movement is different between native and non-native plant species. Mauna Loa, a 13,100 ft. (3,992 m) active volcano on Hawaiʻi Island, experienced a mean annual temperature increase of 1.07 degrees C (1.93℉) between 1970 and 2010, with no detected change in annual precipitation across the gradient, and the authors found it an excellent place to test for species range shifts.

The researchers analyzed long-term vegetation monitoring data from 1970 and 2010 from transects on the southeastern slope of Mauna Loa, Hawaiʻi in order to explore potential shifts in the elevation of both native and non-native plants. To do this, the team re-surveyed 46 vegetation plots in 2010 using the same methodology as the original 1970 surveys, which included collecting presence/absence information and the percentage cover in each vegetation layer (i.e., tree, shrub, and herb layers). To compare shifts in native and non-native species they calculated mean elevation, elevation range, and the upper and lower elevation limits of 69 species that occurred in both the 1970 and 2010 data sets.

The authors found that over a 40-year period, the direction and magnitude of shifts and whether they were driven by changes in the lower, mean, or upper limits depended on the individual species. Strawberry guava shifted its mean elevation ~233 ft. (71 m) upslope due to changes in both its upper and lower limits; weeping-grass had a large increase in mean elevation driven by an increase in its upper limit but not lower limit; molasses grass shifted downward in mean elevation by ~244 ft. (74 m), and Asian sword fern increased in mean elevation with a change in its upper, but not lower elevational limits

Take Home Points

• Individual non-native plant species showed wide variability in their elevation shifts with some species raising their upper elevational limit significantly but not their lower limit (e.g., weeping-grass, Microlaena stipoides), and others increasing both their lower and upper limits (e.g., bamboo orchid, Arundina graminifolia). Some non-native species actually shifted downward over the 40-year period (e.g., red-top grass, Melinis repens).
• The mechanisms driving shifting distributions of non-native plants are largely unknown and could be due to a variety of factors, including: 1) non-native species are still spreading to fill their climate niche, 2) increased disturbances/greater spread (e.g., changing fire regime), 3) enhanced anthropogenic dispersal (building of roads and their use), or 4) changes in habitat suitability due to a changing climate.
• The authors found that native species were generally experiencing shrinking ranges, because the lower limits of their range had increased in elevation and the upper range stayed the same. The authors believe that this stationary upper limit is likely due to the trade-wind inversion (TWI) which abruptly limits rainfall at that higher elevation. In contrast, non-native species experienced a rise in lower and higher elevation limits – perhaps because many non-native species had not yet reached the TWI elevation.

Management Considerations

• Consider increased monitoring efforts that may help detect shifts in non-native plant distributions, especially at the lower and upper elevation limits of species.
• Consider assisting native plant species dispersal across their ranges as conditions change, especially if natural dispersal corridors are absent or degraded. Non-native plants may be able to respond more rapidly to changes in environmental conditions, putting native species at a disadvantage.
• Consider increasing protection efforts for native plants or collecting seeds for future propagation and reintroduction efforts at low elevations, as non-native tree cover is increasing more rapidly than native species cover in these areas.

Summary

Invasive plants that modify ecosystems can harm native biodiversity and degrade important ecosystem services. These species, which are a subset of non-native species, are also likely to be influenced by climate change which could exacerbate impacts. To assess the vulnerability of native ecosystems and federally designated critical habitat in Hawaiʻi to these harmful invaders, the authors used species distribution models to project the current (2013) and future (2100) distribution of 17 particularly detrimental invasive plants across the main Hawaiian Islands. The climate change scenario used in the analysis was the 2080-2100 SRES A1B, which projects a moderately warmer and wetter future. By combining models for multiple invasive species, they projected likely hotspots of non-native species richness and diversity. They used dynamically downscaled projections from the Hawaiian Regional Climate Model, and used three different methodologies (MAXENT, Random Forest, and Gradient Boosting Model), as well as seven bioclimatic and topographic variables, to model species distributions over geographic space. They found that most of the 17 species increased in area under climate change, with higher elevations facing greater invasion risk in 2100.

Results

The area available for occupation by the 17 selected invasive plant species increased by ~11% overall, and by ~12% in federally designated critical habitat in 2100. Invasibility, a metric that includes invasive species richness and diversity, is predicted to increase in Hawaiʻi’s upper elevation areas by 2100. While the majority of invasive species increased in area under climate change, a few species decreased in suitable area at lower elevations.

Management Considerations

• Of the ~8,000 to 10,000 plant species introduced to Hawaiʻi, only about 90 are considered extremely harmful due to their ability to degrade entire ecosystems1. If resources are limited, consider prioritizing the control and prevention of these particularly harmful invaders.
• The distribution of many of the most harmful plant invaders is expected to increase in both area and elevation with climate change. Consider revisiting management goals and objectives as conditions change.
• Consider increasing monitoring efforts in upper elevation native ecosystems for invasive plant species that may be shifting upslope as the climate warms, especially in areas with large concentrations of invasive plant species at lower elevations.
• The quality of current and future projections relies on location data, which is limited for many invasive species. Consider recording both presence and absence location information for invasive species and in areas of both high and low conservation value for use in future modeling efforts.

Take Home Points

• Under increasing temperatures, both native and invasive plant species in Hawaiʻi are expected to shift to upper elevations to find temperature equivalent zones.
• Control of invasive species within and at the boundaries of upper elevation ecosystems will be critical in the coming decades to maintain ecosystem health and integrity.
• Invasive plant species may lose suitable habitat at lower elevations with climate change, though many of these low elevation areas are of marginal value for conservation.
• Given that many critical habitat areas are in high-elevation ecosystems that are vulnerable to invasive species shifts due to climate change, new designations of critical habitat should consider potential climate change impacts.

Summary

Extreme Climatic Events (ECEs) are rare, high-impact events such as hurricanes, heat waves, and extended drought, and they are increasing in frequency and intensity across the Pacific. These extreme events are one of the most immediate threats caused by climate change, and can provide increased opportunities for invasive species to colonize and spread. Despite potentially severe consequences, however, ECEs are rarely considered in planning efforts for ecological restoration. The authors examined the impacts of ECEs on restoration projects and the degree to which they were resilient to ECEs, and they found overwhelmingly negative impacts on restoration efforts. Impacts varied across geographies, species, and within sites, highlighting the need for restoration practitioners to adopt a “portfolio approach” to increase resilience of projects to ECEs. By diversifying the sites, species, and genotypes used as well as the methods employed, managers can reduce the risk of an entire restoration project failing when an extreme event occurs.

Results

Hurricanes and severe storms were the most reported ECEs, impacting 76% of the projects examined via wind, floods, and/or waves. The severity of impacts varied substantially by project and ECEs were not uniform across the restoration site, across all restoration methods, or across species, life stages, or genotypes.  Types of impacts included mortality, community shifts, impacts to reproduction of target species, change in vegetation structure, and changes in species cover. ECEs had overwhelmingly negative impacts on restoration projects, however a few reported both positive and negative impacts or neutral/no-damage impacts. One study reported a positive impact.

Management Considerations

• Plan for ECEs by considering the potential impacts of extreme events most likely to impact your area, possibly exceeding historical events.
• To spread risk through the “portfolio approach”, consider having multiple restoration sites instead of one; place restoration sites across scales (e.g., across elevational or rainfall gradients, or across multiple years or seasons to increase the likelihood of favorable conditions), make use of topographic complexity, and use multiple species.  If possible, identify likely spatial and temporal refugia and incorporate these into project design to reduce the impacts of ECEs.
• Consider selecting a diversity of propagule sources to enhance genetic diversity and adaptive potential to climate change. For example, incorporate species with traits that are more tolerant of extreme conditions such as droughts, heatwaves, or high winds.
• Consider having a post-ECE response plan in place that includes a budget for monitoring and invasive species control. Data on impacts from ECEs can help inform future restoration designs and guide adaptive management.

Take Home Points

• ECEs can create major setbacks for restoration projects by destroying or damaging structures or sites, and by threatening restored species.
• To increase the resilience of restoration projects to ECEs, spread risk across time and space by using the portfolio approach.
• Adapting restoration projects to ECEs or post-ECE recovery may require the use of propagules whose genotypes are more tolerant or resistant to ECEs.
• To adapt to climate change, including to an increasing frequency and severity of ECEs, restoration projects will need to plan for greater uncertainty, secure increased funding for monitoring and adaptive management in response to ECEs, and anticipate setbacks and longer timeframes for success.